/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with this
 * work for additional information regarding copyright ownership. The ASF
 * licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package org.apache.hadoop.hbase.io.encoding;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;

import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.CellComparator;
import org.apache.hadoop.hbase.nio.ByteBuff;
import org.apache.hadoop.hbase.util.ByteBufferUtils;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.yetus.audience.InterfaceAudience;

/**
 * Just copy data, do not do any kind of compression. Use for comparison and
 * benchmarking.
 */
@InterfaceAudience.Private
public class CopyKeyDataBlockEncoder extends BufferedDataBlockEncoder {

    private static class CopyKeyEncodingState extends EncodingState {
        NoneEncoder encoder = null;
    }

    @Override
    public void startBlockEncoding(HFileBlockEncodingContext blkEncodingCtx, DataOutputStream out) throws IOException {
        if(blkEncodingCtx.getClass() != HFileBlockDefaultEncodingContext.class) {
            throw new IOException(this.getClass().getName() + " only accepts " + HFileBlockDefaultEncodingContext.class
                    .getName() + " as the " + "encoding context.");
        }

        HFileBlockDefaultEncodingContext encodingCtx = (HFileBlockDefaultEncodingContext) blkEncodingCtx;
        encodingCtx.prepareEncoding(out);

        NoneEncoder encoder = new NoneEncoder(out, encodingCtx);
        CopyKeyEncodingState state = new CopyKeyEncodingState();
        state.encoder = encoder;
        blkEncodingCtx.setEncodingState(state);
    }

    @Override
    public int internalEncode(Cell cell, HFileBlockDefaultEncodingContext encodingContext, DataOutputStream out) throws IOException {
        CopyKeyEncodingState state = (CopyKeyEncodingState) encodingContext.getEncodingState();
        NoneEncoder encoder = state.encoder;
        return encoder.write(cell);
    }

    @Override
    public Cell getFirstKeyCellInBlock(ByteBuff block) {
        int keyLength = block.getIntAfterPosition(Bytes.SIZEOF_INT);
        int pos = 3 * Bytes.SIZEOF_INT;
        ByteBuffer key = block.asSubByteBuffer(pos + keyLength).duplicate();
        return createFirstKeyCell(key, keyLength);
    }

    @Override
    public String toString() {
        return CopyKeyDataBlockEncoder.class.getSimpleName();
    }

    @Override
    public EncodedSeeker createSeeker(CellComparator comparator, final HFileBlockDecodingContext decodingCtx) {
        return new BufferedEncodedSeeker<SeekerState>(comparator, decodingCtx) {
            @Override
            protected void decodeNext() {
                current.keyLength = currentBuffer.getInt();
                current.valueLength = currentBuffer.getInt();
                current.ensureSpaceForKey();
                currentBuffer.get(current.keyBuffer, 0, current.keyLength);
                current.valueOffset = currentBuffer.position();
                currentBuffer.skip(current.valueLength);
                if(includesTags()) {
                    // Read short as unsigned, high byte first
                    current.tagsLength = ((currentBuffer.get() & 0xff) << 8) ^ (currentBuffer.get() & 0xff);
                    currentBuffer.skip(current.tagsLength);
                }
                if(includesMvcc()) {
                    current.memstoreTS = ByteBuff.readVLong(currentBuffer);
                } else {
                    current.memstoreTS = 0;
                }
                current.nextKvOffset = currentBuffer.position();
            }

            @Override
            protected void decodeFirst() {
                currentBuffer.skip(Bytes.SIZEOF_INT);
                current.lastCommonPrefix = 0;
                decodeNext();
            }
        };
    }

    @Override
    protected ByteBuffer internalDecodeKeyValues(DataInputStream source, int allocateHeaderLength, int skipLastBytes,
            HFileBlockDefaultDecodingContext decodingCtx) throws IOException {
        int decompressedSize = source.readInt();
        ByteBuffer buffer = ByteBuffer.allocate(decompressedSize + allocateHeaderLength);
        buffer.position(allocateHeaderLength);
        ByteBufferUtils.copyFromStreamToBuffer(buffer, source, decompressedSize);

        return buffer;
    }
}
